Flags of Convenience and Shadow-Fleet Flag Cycling

A flag of convenience is the practice of registering a merchant vessel in a state other than that of its beneficial owner, typically to take advantage of lower crewing-wage rules, lighter tax or labour regulation, or thinner corporate-disclosure requirements. The practice is older than sanctions enforcement — the modern model dates to Panama's 1916 register and Liberia's 1948 register — and most of the world's blue-water tonnage flies under one. In a sanctions-OSINT context, what matters is not the existence of open registries but the way Russia's shadow tanker fleet has cycled vessels through a predictable sequence of them between 2022 and 2026, using each re-flagging as a fresh window of ambiguity for port-state control. This page explains the underlying institutions — the Paris MoU performance tiers, the IMO registration framework, the registries themselves — and sets out a four-step open-source method for detecting cycling on a suspect hull.

What a flag of convenience is

Article 91 of the UN Convention on the Law of the Sea requires a "genuine link" between a vessel and its flag state but does not define the term, and in practice the threshold for registration in an open registry is low.^[1] Panama formalised the model in 1916; Liberia, with US backing, followed in 1948 and rapidly became the world's largest open registry through the 1960s.^[2][3] The economic rationale is straightforward: a beneficial owner can crew the vessel under the flag state's wage rules (often lower than those of the owner's home jurisdiction), pay tonnage tax under the flag state's regime (often a flat fee per gross tonne), and submit to the flag state's safety and labour inspection cadence (often lighter than that of a traditional maritime nation). The arrangement is lawful and ubiquitous — roughly three quarters of the world's tonnage is registered under flags considered "open" by the International Transport Workers' Federation.^[4]

Legitimate uses dominate the population. Open registries underpin most of the global container and bulk fleet; the largest container lines run their hulls under Panamanian, Liberian and Marshall Islands flags as a matter of course. What makes a particular flag listing a sanctions-OSINT concern is the combination with other indicators — opaque ownership, non-IG insurance, AIS gaps, voyage patterns through known ship-to-ship transfer anchorages, and shipment of price-capped or sanctioned cargo — not the flag itself.

The Paris MoU performance tiers

The Paris Memorandum of Understanding on Port State Control, signed in 1982 and now covering 27 maritime authorities across Europe and the North Atlantic, publishes an annual performance ranking of flag states based on three calendar years of port-state inspection and detention data.^[5] Each flag is sorted into a White, Grey or Black tier. White-tier flags have low detention ratios and are inspected at a reduced frequency; Grey-tier flags are inspected at the standard cadence; Black-tier flags are inspected more frequently and, after repeated detentions, may be banned from Paris MoU ports under the Refusal of Access procedure. The Tokyo MoU operates a parallel system for the Asia-Pacific region with comparable methodology.^[6]

For shadow-fleet detection the performance tier is a useful first filter. A tanker whose current flag is on the Paris MoU Black list, or has been within the last three reporting periods, carries a baseline elevated-risk score before any vessel-specific OSINT work is done. Most of the registries that have absorbed shadow tonnage between 2022 and 2026 — Cameroon, the Comoros, Palau, Sierra Leone, Togo, Tanzania (Zanzibar) — sit on the Paris MoU Black or Grey tier. A handful (the Cook Islands, San Marino) appear on the Grey tier with limited recent inspection history because their fleets were small until recently.

The shadow-fleet flag cycle, 2022 to 2026

The observable pattern across the published KSE Institute, CREA, Windward and Lloyd's List reporting is that shadow-fleet tankers move through flags in a predictable sequence, with each re-flagging triggered by a sanctions event or by pressure on the previous registry.^{[7][8][9][10]} A representative cycle:

1. Liberia or Marshall Islands — the established open registries where a vessel was held before war or before its operator became sanctions-relevant. Both registries have, since 2023, tightened their willingness to flag tonnage with Russian-counterparty links, and have deregistered vessels under OFAC and EU pressure.
2. Gabon or Cameroon — smaller African registries with thin oversight, often administered by private operators in third countries (the Gabonese register is operated from the UAE). These absorbed a wave of deflagged tonnage through 2023 and into 2024.
3. Cook Islands, Palau, San Marino, Comoros — specialist smaller registries that absorbed further re-flaggings in 2024. The Cook Islands undertook material deregistrations following the Eagle S anchor-drag incident of December 2024 and subsequent diplomatic exchanges.^[11] Palau publicly committed to removing identified shadow-fleet vessels from its register.^[12]
4. Russian state flag — from late 2024 and through 2025, a growing share of vessels re-flagged back to Russia itself, on the apparent basis that an overt Russian flag offered greater predictability than a flag of convenience subject to western diplomatic pressure. The KSE Institute Russian Shadow Fleet Tracker recorded the Russian-flag share of shadow tonnage rising from approximately 3 percent to 21 percent over a nine-month window.^[7]

The cycle is not deterministic — vessels skip steps, double back, or move sideways between similarly tiered registries — but the overall arc from established open registry through smaller open registries and ultimately, for the most exposed tonnage, to the Russian state flag is the dominant 2022 to 2026 pattern.

Highest-risk registries in 2026

As of 2026, the registries that recur most often in published shadow-fleet identifications, beyond the Russian state flag itself, include:

• Gabon — register administered privately from the UAE; minimal public disclosure of beneficial ownership; carried a disproportionate share of vessels with definitive group-owner links to Russia through 2024 and 2025.^[9]
• Cameroon — identified by Windward as flagging approximately 13 percent of the dark fleet at peak; publicly committed in 2024 to a crackdown, with mixed downstream evidence of execution.^[12]
• Comoros — absorbed re-flaggings after 2024 as Cook Islands and Palau tightened.
• San Marino — landlocked-state open registry, marginal until 2023, absorbing a steadily increasing share of mid-tier tanker tonnage.
• Post-deregistration aftermath — after the Cook Islands deregistered vessels following the Eagle S incident, the displaced hulls migrated to Comoros, Cameroon, and the Russian flag within weeks.^[11]

How to detect flag cycling from open sources

The methodology below applies to any vessel where shadow-fleet conduct is suspected. It uses entirely public sources.

Limitations

Open-source flag-cycling analysis has three durable limits. First, several of the registries that absorb shadow tonnage — Gabon, Comoros, Cameroon — are administered by private operators based in third countries (typically the UAE) and do not publicly disclose ultimate beneficial ownership, vessel-by-vessel registration certificates, or the corporate identity of the registered owner. The flag history is observable from Equasis and GISIS; the ownership behind it often is not.

Second, a flag-state revocation does not, in itself, bind on third-country port-state control. When the Cook Islands deregisters a vessel, the vessel can re-flag elsewhere within weeks and continue to call at non-Paris-MoU ports under the new flag without interruption. The enforcement consequence of a deflagging accrues only at Paris MoU and Tokyo MoU member ports, and only after the new flag's performance data has accumulated.

Third, the Paris and Tokyo MoU performance tiers lag by up to three years — the rankings are calculated from three rolling calendar years of inspection data. A newly absorbed shadow-fleet vessel under a previously low-volume flag (San Marino, Comoros) may not produce sufficient inspection volume to move the flag's tier until the cycling has already shifted to the next registry.

Related methodology and datasets

This page sits within a wider set of [0x]INT shadow-fleet methodology resources. The case-study companion piece is Russia's Shadow Fleet: How 287 Sanctioned Tankers Keep Urals Crude Flowing, which walks through three named case studies and the full investigative pipeline. The underlying field schema and IMO-level cross-list aggregate is published as the Russia Shadow Fleet Tanker Cross-List Dataset under CC-BY-4.0. Adjacent methodology pages cover ship-to-ship transfer detection and AIS gap analysis; for the latest flag-state churn across the fleet, see our 2026 dark-fleet intelligence brief, and the broader sanctions framework is treated in our EU 20th-package CASP ban briefing.

Sources and further reading

1. United Nations Convention on the Law of the Sea, Article 91 (Nationality of ships).
2. International Maritime Organization — flag state implementation framework.
3. Liberian International Ship and Corporate Registry (LISCR) — registry history and corporate background.
4. International Transport Workers' Federation — Flags of Convenience watch list.
5. Paris MoU on Port State Control — Annual Report (Performance List, White/Grey/Black tiers).
6. Tokyo MoU on Port State Control — Annual Report.
7. Assessing Russia's Shadow Fleet. Kyiv School of Economics, KSE Institute, June 2024. Russian-flag share trend.
8. Policy briefing: tackling the Russian shadow fleet. Centre for Research on Energy and Clean Air (CREA), August 2024.
9. Hundreds of shadow fleet ships sail under a false flag. Follow the Money — investigative reporting on Gabon and Panama registries.
10. Finland police seize Russian-linked dark fleet tanker Eagle S. Lloyd's List, 26 December 2024.
11. Cook Islands Politicians Question Role Supporting Shadow Fleet. The Maritime Executive — Cook Islands registry deregistrations and the Eagle S incident.
12. Cameroon Pledges Crackdown on Ship Registry Flagging 13 percent of Dark Fleet Tankers. Windward.
13. Equasis — IMO-backed open-access ship information database.
14. IMO Global Integrated Shipping Information System (GISIS) — ShipDB module.
15. U.S. Treasury Designates Sovcomflot. Treasury press release JY2121, 23 February 2024 — reference point for flag-cycling cascades following major OFAC actions.
16. EU 14th sanctions package vessel listings (Council Regulation amending 833/2014). European Commission, June 2024.